It is useful to first discuss the improvements in synthetic bristles. In mankind's long history of utilizing natural materials, considerable application has been made of relatively coarse hairs, filaments and fibers of animal and vegetable origin. Bristle is a common term for these materials, although the term is often restricted to mean animal hair, and even more specifically, sometimes to the hair of the swine. In the context of this disclosure, I use the term bristle in its broadest sense to cover all naturally derived filamentatious material which can be used to make the flexible brushing portion of a brush. I further define a brush as a device, composed of a multiplicity of bristles in which the base material in at least a portion of the bristles is a synthesized polymer, co-polymer, alloy, or mixtures, e.g., nylon, polyester, polyolefin, Amalon, or Esterlon. As will be recognized by those skilled in the art, Amalon is a mixture of polyolefin and nylon, and Esterlon is a mixture of polyester and nylon.
Since the development of the first truly synthetic bristle (nylon) as an adaptation of synthetic fiber technology after World War II, a number of other synthetic bristle adaptations have been developed and commercially employed. These synthetics have displaced natural bristles in some brush applications. However, natural bristles are still important materials in the brush industry because the synthetics developed to date have not been completely satisfactory substitutes. On the other hand, some of the synthetics provide certain superior properties to the natural bristles for some applications (e.g. improved water resistance and abrasion resistance).
One objective of this invention is to provide synthetic bristles which have not only the aforementioned benefits of such synthetics, but also many of the attributes of natural bristles never before available in synthetic versions.
A second objective of this invention is to provide a synthetic bristle superior to conventional synthetics in terms of polymeric material utilization efficiency.
A third objective is to provide a synthetic bristle which is opaque, or nearly opaque, to light without requiring pigmentation or by using significantly less pigmentation than conventional synthetics.
Natural bristle materials, whether of vegetable or animal origin, result from organic growth processes wherein elongated cellular formations build upon one another to form essentially rod-like structures of sufficient resilience and integrity to serve the functional needs required in brushes for painting, powdering, scrubbing, sweeping and the like. It is the cellular wall formation that provides structural character to these natural bristles along with the complex chemical makeup of the specific bristle. Some natural bristles are essentially tapered in that one end (the butt end) of the bristle is larger than the other (tip end). Still others are not tapered or have very little of this tendency. Natural bristles are always irregular in shape along their length, and have scale-like outer surfaces. Some of these are naturally split at the end, forming tiny fingers which are useful in brush performance.
Synthetic bristles heretofore available have none of the cellular structures, shape irregularities or scale-like surfaces. Rather, they have dense polymeric structure and are highly uniform in shape, with smooth surfaces. Synthetic bristles are available in tapered or untapered form, and in cross-sectional profiles of solid round, hollow round, ribbed, S shaped and other shapes dependent on extrusion technology. All synthetics to date require physical splitting of the ends (flagging) where this is deemed desirable in brushes.